Re: Vanilla-Kernel 3 - page allocation failure

[David Rientjes]

On Thu, 27 Oct 2011, Philipp Herz - Profihost AG wrote:

> > It won't be triggered synchronously in this context since it's a
> > GFP_ATOMIC allocation, which is why it emits a page allocation failure in
> > the first place, but it will show whether defragmentation is the issue or
> > you're just simply low on memory.
> Do you mean that "memory compaction" should be turned off again?
> 

No, I mean the difference since 2.6.32 might be that lumpy reclaim was 
deprecated so it is no longer causing high-order page allocations to be 
free in atomic context where no balancing or migration can synchronously 
be done.

> How can I see the difference between "deframentation issue" and "low memory"?
> I did not get this point.
> 

unusable_index and extfrag_index in debugfs if you've enabled and mounted 
that.  You could also take a look at tweaking 
/proc/sys/vm/extfrag_threshold, see Documentation/sysctl/vm.txt.
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